Lighting for homes, offices, commercial spaces, and public areas may be controlled to account for occupancy and ambient light at the light fixture, workstation, room, floor and building levels. Various systems have been implemented using the Digital Addressable Lighting Interface (DALI) which is a global standard for a lighting control data protocol and transport mechanism maintained as IEC 62386. The DALI standard specifies a two wire, bi-directional data bus connecting a DALI application controller with up to 64 DALI control gear items and control devices, such as ballasts, drivers, transformers, occupancy sensors, photo sensors, wall switches, and dimmers. The data bus cable is mains rated and may be run next to mains conductors or in a cable with mains conductors. The DALI control gear are individually addressable and data is transferred between the application controller and the control gear using an asynchronous, half-duplex, serial protocol. Data is transmitted using Manchester encoding at a fixed data transfer rate of 1200 bits/s to ensure reliable communications. The DALI bi-directional data bus also provides power at 16 volts and 250 mA maximum current. DALI application controllers and control gear may be connected in a star or daisy chain configuration.
FIG. 1 shows a block diagram of an exemplary DALI system 100. An application controller 105 is connected to a number of control gear items 1100-11063 by the bi-directional data bus 115. Control gear items 1100-11063 may control light sources 125 or other equipment. Mains power is provided through mains cable 120. In some implementations, mains power is provided by or controlled by application controller 105.
FIG. 2 shows a schematic diagram of at least a portion of an exemplary DALI control gear 205 similar to control gear 1100-11063. DALI control gear 205 may include a bus interface 210 and operating circuitry 215. Bus interface 210 may isolate the operating circuitry 215 from the bi-directional data bus 115 using a diode bridge 240 and optocouplers. For example, optocoupler 220R may be used for receiving commands or messages from application controller 105 to the control gear 205, while optocoupler 220T may be used for transmitting responses and messages from the control gear 205 to the application controller 105. The control gear 205 may include a computer 225, for example, a single chip microcontroller with a processor and memory 230 for exchanging information over the DALI bi-directional data bus 115 and for controlling lamps and other lighting equipment.
FIG. 3 shows a schematic diagram of at least a portion of an exemplary power supply 300 for providing power to DALI control gear circuitry. The exemplary supply is capable of providing one or more outputs, for example, +5V and Vcc. The exemplary control gear power supply 300 includes a partially shown rectifier circuit 305 and switches 310, 315, and 320. While switches 310, 315, and 320 may be implemented as semiconductors, for example, transistors, field effect transistors (FETs), metal oxide semiconductor field effect transistors (MOSFETs), in this example, switches 310, 315, and 320 are N-channel MOSFETs.
After initial turn on, the +5V supply may be generated directly from an output 325 of the rectifier circuit 305 and the Vcc supply may be generated from the output 325 through switch 310 controlled by switches 315 and 320. After the output 325 stabilizes and Vcc is established, the supplied control gear reaches steady state operations, that is, operations that implement DALI functions. At some point, a standby signal may be received at input 330. Upon receipt of the standby signal, switch 315 will conduct, forcing the gate of switch 310 to a level causing switch 310 to open, removing power from Vcc. In addition, switch 320 will conduct, forcing Vcc to a low level. In this example, when the standby signal received, the +5 v supply remains at full power capacity and Vcc is substantially disabled.
DALI standards set limits on circuit initialization times after power is applied. In addition, DALI standards also set limits on power consumed by control gear components during different modes of operation after initialization is complete. For example, power consumption may be held at a lower level when the control gear is operating in standby mode.
It would be advantageous to provide a power supply capable of operating in various modes, for example, an increased power mode that allows control gear components to complete initialization during a specified time period, and a decreased power mode that limits power available to control gear components after initialization and when operating in standby mode.